Method of making an electrical resistor



1969 A. N. R. Wl TDOECKT 3,427,712

METHOD OF MAKING AN ELECTRICAL RESISTOR Filed June 25, 1964 Mam m? 416527 A4 W/mascxr United States Patent METHOD OF MAKING AN ELECTRICALRESISTOR Albert Norbert Robert Witdoeckt, 9a Witte Nonnenstraat,

Oostende, Belgium Filed June 25, 1964, Ser. No. 377,809 Claims priority,application Belgium, July 9, 1963,

634,716; May 6, 1964, 647,596

US. Cl. 29-611 3 Claims Int. Cl. H01c 7/04, 3/00 ABSTRACT OF THEDISCLOSURE Electrical resistors are made by applying to an insulatingbacking a thin aluminum sheet having a thickness less than 0.010 mm.,and then cutting the aluminum sheet but not its insulating backing bymeans of knives that rotate about axes perpendicular to the line of cut,thereby to form in the aluminum sheet a multiplicity of cuts that extendin from alternately opposite edges of the sheet and that provide agreatly elongated zigzag path of electrical resistance.

The present invention relates to an electrical resistor in particularfor use as heating element, constituted of a rolled, conductive metallicsheet adhering by one of its faces to an insulating support or a supportcovered with insulating material, having gaps extending so as to form anelectrical circuit at the ends of which are disposed connectingterminals.

In known electrical resistors of this type, the conductive sheet is acopper sheet of minimum thickness 0.025 mm., having a single gapextending spirally or with some similar broken outline from its centralpart to its marginal part.

In order to be able to facilitate manufacture of the resistor and toreduce its cost price, use is made in the invention of an aluminum sheetless than 0.010 mm. thick.

In an embodiment of the invention the new resistor has gaps which areparallel to each other and which extend alternatingly from. one edge ofthe conductive sheet to the vicinity of the opposite edge of the sheet,and from thereto the vicinity of the first-mentioned edge, thisarrangement of the gaps being simple, quick and economical to carry out.

The invention further concerns a process for manufacturing the newresistor, in accordance with which a conductive sheet of rolled metal,constituting the resistor, is caused to adhere to an insulating supportor a support covered with insulating material, whereupon gaps are madein the conductive sheet so as to form an electrical circuit therein, andfinally, terminals are attached to the ends of the circuit thusconstituted.

In accordance with an important feature of the said process, acontinuous strip of rolled metal, constituting the resistor, is causedto adhere to an insulating strip or strip covered with insulatingmaterial, this strip being continuous and flexible and constituting thesupport. Thereupon the above-mentioned gaps are made in the sheet, toproduce electrical circuits; the strips connected to each are cut, so asto separate the circuits and the above-mentioned terminals are attachedto each of them. This feature makes it possible to manufacture theresistor from a roll of the metallic strip and a roll of the insulatingstrip, to stick the unwound strips together, to mark out continuouslythe gaps required, to wind up the resistors thus obtained and to cutthem off as need arises, the connecting terminals then being attached,whereupon they are ready for use.

3,427,712 Patented Feb. 18, 1969 However, in accordance with anotherembodiment of the invention, it is also possible to manufacture the newresistor by causing a conductive sheet of rolled metal, constituting theresistor, to adhere to an insulating support or a support which iscovered with insulating material and which may for example be rigid,having dimensions generally speaking greater than those of theconductive sheet, whereupon the above-mentioned gaps are made and theconnecting terminals are attached.

The making or marking of the parallel gaps extending alternately fromone edge of the conductive sheet to the vicinity of the opposite edge ofthe sheet, and from there to the vicinity of the first-mentioned edge,is obviously a simple and practicable matter, and can be carried out byone related movement of the working tools and the conductive sheet. Itis possible to make gaps going from one edge to the other of theconductive sheet, and, by reversing the tools or the conductive sheet,to make the return gaps.

The gaps are made in accordance with the invention by mechanicallytaking out material from the conductive sheet.

The invention will now be described with the aid of the attacheddrawing, which show diagrammatically and by way of example only twoembodiments of the present invention.

FIGURE 1 is a perspective view of an embodiment of the resistor of theinvention.

FIGURE 2 is a diagram illustrating a process for making the resistor ofthe invention.

FIGURE 3 is a diagram illustrating a second embodiment of the resistorof the invention.

In the various figures like numbers are used to designate like parts.

The resistor of the invention is constituted of a conductive sheet 1, ofthin, rolled aluminum sheet less than 0.010 mm. thick in particular, ofthicknesses between 0.003 mm. and 0.010 mm.

The conductive sheet 1 adhers by one of its faces to an insulatingsupport 2 or a support covered with insulating material. The dimensions,that is to say the length and width, of the support are restricted andare generally greater than those of the conductive sheet 1.

The insulating support sheet 2 can be flexible or rigid, and is somewhatthick, in relation to the conductive sheet 1. The support sheet can beconstituted of a sheet of paper, cardboard, synthetic material, tissue,or it may be a plate consisting of plaster, compressed asbestos cement,glass, mica; further it may be a metallic plate covered with insulatingmaterial, such as vitrified enamel, or a concrete plate covered withinsulating material, the above list of examples not being intended to berestrictive.

The conductive sheet 1 has parallel gaps, as for example thelongitudinal gaps 3 and 4 which define an electrical circuit, formed inthe example chosen of a conductor in the form of a strip folded inzag-zag. Electrical terminals 5 are attached atthe ends of the circuitfor the supply of current. It should be understood that the longitudinalgaps 3 and 4 can be replaced by similar transverse gaps.

The gaps 3 extend from a transverse edge 6 of the conductive sheet 1 tothe vicinity of the opposite transverse edge 7 of the said sheet in sucha way that they do not reach the edge 7 and are spaced therefrom by thedistance marked a in the drawings.

The gaps 4 extend between the gaps 3, from the edge 7 to the vicinity ofthe edge 6, without however actually reaching this, and are spaced fromthe edge 6 by the distance marked b in the drawings, generally speakingequal to the distance a.

1 The gaps '3 and 4 extend side by side fora-length marked 0, foundbetween a and b.

To manufacture the electrical resistor described above, the conductivesheet 1 is caused to adhere, for example by glueing, to the support 2,whereupon, by cutting, gaps 3 and 4 are made simultaneously orsuccessively in the sheet 1 and connecting terminals 5 are attached tothe sheet 1.

To cut out simultaneously the gaps 3 and 4, rotary knives are applied atthe length 12 against the conductive sheet 1 at the localities of thegaps 3. Thereupon, along the length c, the knives are continouslyapplied against the sheet 1 at the localities of the gaps 3, whereas orother knives are applied against the sheet 1 at the localities of thegaps 4. Finally, at the length a the knives cutting the gaps 3 cease tobe applied against the sheet 1, whereas the other knixes concerned withthe gaps 4 are applied right up to the edge 7. Accordingly, the gaps 3and 4 are cut in one movement of the said working tools,

from the edge 6 of sheet 1 to the edge 7 of the said sheet.

To cut the gaps 3 and 4 simultaneously, accordingly two sets of workingtools can be used. The set of tools concerned with the gaps 3 are movedfrom the edge 6 toward the edge 7, applying against the sheet 1 on thepaths b and 0, whereas at the same time the set of tools concerned withthe gaps 4 are moved from the edge 7 towards the edge 6, applyingagainst the sheet 1 on the paths a and c.

To cut the gaps 3 and 4 alternately, use is preferably made of sets ofrotary knives, which are applied along the length b and 0 against theconductive sheet 1, but are removed from contact with this at the lengtha. Thereupon the knives are lifted off, perpendicular to the gaps, i.e.,following the arrow X, to be reapplied at a distance equal to thespacing of the gaps 3 and 4. The knives are then applied along thelengths a and c against the conductive sheet 1, and are removed fromcontact with this at the length b. Accordingly, the gaps 3 are cut byone movement of the cutting tools from the edge 6 toward the edge 7,whereupon the gaps 4 are cut by the reverse or return movement of thesecutting tools.

In the processes described above it is the knives which are moved, butthe invention is also concerned with the case in which the knives remainstationary and act on the conductive sheet which moves.

When a flexible continuous strip is used as conductive sheet and asinsulating support, it is preferable to manufacture the resistors of theinvention from a roll of the conductive strip and a roll of theinsulating strip, said rolls are unwound and stuck together, the gapsbeing made simultaneously as described above, to make the successiveelectrical circuits. The strips with the marked gaps can be wound up andsubsequently cut in accordance =with"the'-said circuitsflto obtainindividual resistors to which are attached the connecting terminals.

It is obvious that the invention is not exclusively restricted to thetwo embodiments shown, and that numerous modifications can be made inthe shape, thearrangement and the construction of some of the elementsused in the carrying out of these embodiments, provided that thesemodifications do not contradict the aim of any of the following claims.

What I claim is:

1. A process for manufacturing an electrical resistor, comprisingfeeding an aluminum sheet having a thickness less than 0.010 mm. onto aninsulating support and adhering said sheet to said support, cuttingthrough said aluminum sheet but not through said insulating support bymeans of rotating knives to form parallel gaps extending alternatelyfrom opposite edges of the aluminum sheet by causing movement of saidsupport and the axes of said knives relative to eachother in a directionparallel to the length of said gaps, and adding electrical terminals tothe ends of the resistor constituted by the cut aluminum sheet. 1

2. A process as claimed in claim 1, and thereafter imparting to saidknives and said insulating support relative movement in a directiontransverse to the length of said gaps to position said sheet and saidknives relative to each other for the formation of further said gaps.

3. A process as claimed in either of claims 1 and 2, in which saidcutting is performed by use of two series of rotating knives with onesaid series cutting the said gaps that open through one said edge of thesheet and the other said series forming the gaps that open through i theother said edge of the sheet.

References Cited UNITED STATES PATENTS 2,680,184 6/1954 Cox 219-383 x2,719,213 9/1955 Johnson 338212 3,149,406 9/1964 Eisler 29-155.53,172,074 3/1965 Drewes et a1. 338-308 2,622,178 12/1952 Glynn 29-620 X3,031,745 5/ 1962 Dzialo. 3,119,919 1/1964 Pratt. 3,162,076 12/ 1964Emerson et a1 83--678 X FOREIGN PATENTS 584,588 10/1959 Canada.

JOHN F. CAMPBELL, Primary Examiner.

J. L. CLINE, Assistant Examiner.

US. Cl. X.R.

